The invention relates to packaging assemblies for containing, transporting, and storing hazardous substances. More particularly, the invention relates to packaging assemblies that employ rotationally molded overpacks hermetically sealed by spin welding and which employ pour-in-place foam to secure the hazardous substance within the overpack.
Rotationally molded overpacks for enclosing 55 gallon drums and a spin welding apparatus employable for hermetically sealing same are disclosed by Samuel Unger et al. (U.S. Pat. No. 4,784,709), incorporated herein by reference. Unger et al. disclose that a 60 gallon overpack formed by a low precision rotational molding technique using thermoplastic resin can be employed to hermetically seal a 55 gallon drum with a high performance closure by a spin welding process using a special spin welding apparatus. In particular, the spin welding apparatus disclosed by Unger et al. is capable of absorbing high vibrational loads while spin welding a large imprecisely molded overpack. The resultant spin weld is seamless and has a high performance. A properly configured spin weld may have a strength which is equal to or in excess of the strength of unmodified portions of the wall of the overpack. Accordingly, 55 gallon drums holding toxic material may be safely transported and securely stored in such spin welded overpacks for long periods of time.
Since commercial rotational molding facilities are more widely available as compared to precision injection molding facilities and since the rotational molding technique is more easily and cheaply implemented as compared to the precision injection molding technique, rotationally molded overpacks may often be fabricated more cost effectively at facilities near clean-up sites having leaky and/or potentially leaky 55 gallon drums. If a mobile spin welding apparatus as described by Unger et al. is brought to a clean-up site, leaky 55 gallon drums at the clean-up site may be hermetically sealed in situ within locally produced rotationally molded overpacks with high performance spin welds. Such use of local facilities and resources reduces transportation costs and enhances the cost effectiveness of the operation.
A number of other articles may be similarly sealed within such spin welded overpacks and transported to a disposal site. However, it is disclosed herein that, if a spin welded overpack is employed to stabilize a heavy article, especially one having a sharp projecting element, such an overpack may be susceptible to being punctured during a drop test that qualifies the assembly for safe transportation. Electrical transformers containing high levels of toxic materials such as polychlorinated biphenyls (PCB's) require safe containerization. Often such transformers include projecting elements. A transformer with projecting elements provides one example of an article which could be sealed within a spin welded overpack but which also has a capability of puncturing the same overpack in which it is contained. Accordingly, the employment of an unmodified spin welded overpack for securing disposal of a transformer that may leak PCB's is sometimes not recommended due to the risk of puncture and the release of such PCB's into the environment. What was needed was a modified overpack which could be employed for handling the disposal of articles such as transformers which often are capable of puncturing unmodified forms of the overpack.